1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to accessory assemblies for electrical switching apparatus, such as circuit breakers.
2. Background Information
Electrical switching apparatus, such as circuit breakers, as well as transfer switches, network protectors and the like, are often equipped with accessories such as, for example and without limitation, auxiliary switches, shunt trip devices, under voltage release devices, and bell alarms. Such devices can be employed in a variety of ways to provide signals indicating certain conditions within the apparatus and/or to initiate a change in status of the apparatus such as, for example, to trip open the separable contacts of the apparatus in response to an electrical fault condition (e.g., without limitation, current overload; short circuit; abnormal voltage).
In view of the increasing market trend to reduce the overall size of the circuit breaker, the space which is available within the circuit breaker housing is limited. In addition to size constraints, the location available for mounting accessories within the circuit breaker can also be problematic. For example, some locations for mounting the accessories in the circuit breaker have limited access for installing the accessories and, in some instances, blind installation is required, wherein it is not possible to see the accessory to mount the accessory within the circuit breaker housing. As a result, incorrect installation and/or damage to the accessories can result, and safety features of the circuit breaker can be adversely affected.
Another difficulty which must be addressed is how to efficiently and effectively mount and secure the accessories in the proper orientation within the allotted space in the circuit breaker. Using fasteners, such as threaded screws, is undesirable for a number of reasons. Among them is the fact that the screw, if it were to become loose, could become lodged in the circuit breaker mechanism. Such fasteners also constitute an additional separate part having an associated added cost, and they require the use of a separate tool, such as a screw driver, to effectuate the installation or removal of the accessory. Furthermore, they are typically threaded into plastic (e.g., without limitation, the molded housing of the circuit breaker). Over time, repeated insertion and removal of the fastener may cause the threads in the plastic to strip.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in accessory assemblies therefor.